JP3479558B2 - Heat shrinkable polyester film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polyester film used for various packaging materials and the like. The present invention relates to an excellent heat-shrinkable polyester film without unevenness. 2. Description of the Related Art Heat-shrinkable plastic films are used for marking, protection, etc. of containers, fishing rods, condensers, rod-shaped fluorescent lamps and the like.
In addition to being used for binding and improving the added value of products, it is used for stacking and close-packing books and notebooks. At present, various applications are expected in many other fields utilizing the shrinkage and shrinkage stress of this heat-shrinkable film. Conventionally, as a material of a heat shrinkable film,
Resins such as polyvinyl chloride, polystyrene, and polyolefin have been used. However, such resins have disadvantages in heat resistance, weather resistance, chemical resistance and the like. For example, although a polyvinyl chloride film can be made into a heat-shrinkable film having various shrinkage characteristics, fish eyes are likely to occur frequently, and a product using a film printed on this as a packaging material is impaired in aesthetic appearance and has a reduced product value. It was easy to become. Also, in order to obtain a heat-shrinkable film without fish eyes, excessive quality control is required,
There was a problem that the film manufacturing cost was significantly increased. In addition, polyvinyl chloride can cause pollution problems when incinerated at the time of disposal, and plasticizers and other additives in the polyvinyl chloride resin bleed out over time, causing dirt due to the adhesion of dust and the like. It was not preferred in terms of sex. On the other hand, a heat-shrinkable film obtained from polystyrene has a good finish after shrinkage, but has a low solvent resistance, so that a special ink must be used at the time of printing, and even at room temperature. It had to be stored in a cool place for natural shrinkage to occur. In addition, it requires incineration at a high temperature and generates a large amount of black smoke and an unpleasant odor at the time of incineration. As a material capable of solving these problems, a polyester film is highly expected, and its use has been remarkably increased. [0005] Heretofore, heat-shrinkable polyester films have not been sufficiently satisfactory in heat-shrinkability. In particular, shrinkage unevenness tends to occur during shrinkage, and characters and patterns printed on the film cannot be reproduced well when the film is shrunk to cover PET bottles, polyethylene bottles, glass bottles, etc. There were problems such as missing.
In response to such a demand, as described in Japanese Patent Application Nos. 4-110963 and 4-110964, a polyester resin obtained by copolymerizing a specific copolymer component is used. A heat-shrinkable polyester film or the like in which shrinkage unevenness is reduced by controlling the shrinkage speed has been proposed. However, such a heat-shrinkable polyester film has a property of shrinking at a relatively low temperature, and is suitable for shrink-coating a container such as a glass bottle which shrinks at a high temperature exceeding 100 ° C. Have had problems such as uneven shrinkage due to rapid shrinkage and poor heat resistance. An object of the present invention is to provide an excellent heat-shrinkable polyester film which is excellent in shrinkage characteristics at a high temperature and has no shrinkage unevenness and remains. [0007] In view of such circumstances, the present inventors have made intensive studies on the polyester resin constituting the heat-shrinkable film, and have reached the present invention. That is, the heat-shrinkable polyester film of the present invention comprises a polyester resin comprising an acid component mainly containing naphthalenedicarboxylic acid or an ester-forming derivative thereof and an alcohol component mainly containing ethylene glycol. The above-mentioned trihydric or higher polyhydric alcohol as the polyhydric carboxylic acid and / or alcohol component accounts for the ratio (A mol%) of the trihydric or higher polyhydric carboxylic acid in the total acid component and the total alcohol component. The sum of (A + B) and the ratio (B mol%) of the trihydric or higher polyhydric alcohol is in the range of 0.01 to 1 mol%. The polyester resin used in the heat-shrinkable polyester film of the present invention comprises an acid component containing naphthalenedicarboxylic acid or an ester-forming derivative thereof as a main component and an alcohol component containing ethylene glycol as a main component. As an acid component constituting the polyester resin, a naphthalene dicarboxylic acid such as naphthalene-1,4- or -2,6-dicarboxylic acid or an ester-forming derivative thereof is contained in a proportion of 50 mol% or more in the total acid component. And preferably at least 60 mol%, more preferably at least 70 mol%. This is because if the content of naphthalenedicarboxylic acid is less than 50 mol%, the mechanical strength at the time of forming a film decreases, and the glass transition temperature of the polyester resin decreases, and the shrinkage property at high temperatures decreases. To do that. [0010] Acid components other than naphthalenedicarboxylic acid that can be used in the present invention include aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, and fatty acids such as glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid and succinic acid. Group dicarboxylic acids or their ester-forming derivatives. Among these, from the viewpoints of film forming properties, mechanical strength, shrinkage characteristics at high temperature, etc., aromatic dicarboxylic acid or its ester-forming derivative is contained in the total acid component as a total amount with naphthalenedicarboxylic acid.
The content is preferably at least 85 mol%, more preferably at least 85 mol%. The aliphatic dicarboxylic acid or its ester-forming derivative is used for the purpose of increasing the heat shrinkage of the film, and is less than 20 mol% in the total acid component.
Preferably, it can be contained in a range of less than 15 mol%. This is because when these aliphatic dicarboxylic acid components are contained in an amount of 20 mol% or more, the mechanical strength of the polyester film may be reduced. The alcohol component constituting the polyester resin contains ethylene glycol in a proportion of 50 mol% or more in all the alcohol components, and preferably in a range of 60 mol% or more. This is because if the content of ethylene glycol is less than 50 mol%, the polymerization reactivity tends to decrease when producing the resin, and a resin having the desired degree of polymerization may not be obtained. is there. The alcohol component other than ethylene glycol which can be used in the present invention includes cyclohexane dimethanol, propylene glycol, triethylene glycol, diethylene glycol, neopentyl glycol, polyethylene glycol, polyoxytetramethylene glycol, bisphenol compound or a bisphenol compound thereof. Examples include ethylene oxide adducts of derivatives. These other alcohol components can be used in a range that does not impair the effects of the present invention, for example, in a range of 20 mol% or less. In the present invention, the sum of the ratio of the acid component other than naphthalenedicarboxylic acid in the total acid component and the ratio of the alcohol component other than ethylene glycol in the total alcohol component is in the range of 10 to 50 mol%. Preferably, there is. This is because the sum of the ratio of the acid component other than naphthalenedicarboxylic acid in the total acid component and the ratio of the alcohol component other than ethylene glycol in the total alcohol component is 10 mol%.
Below, there is a tendency that sufficient solvent adhesion is not obtained,
Conversely, if it exceeds 50 mol%, the solvent resistance of the film itself tends to be inferior or a resin capable of forming a film tends not to be obtained, more preferably in the range of 20 to 40 mol%. In the present invention, rapid shrinkage is suppressed,
For the purpose of further reducing shrinkage unevenness, one or more polyhydric carboxylic acids or polyhydric alcohols having three or more valences are used as an acid component or an alcohol component. Specific examples of trivalent or higher polycarboxylic acids or polyhydric alcohols include:
Examples thereof include polycarboxylic acids such as trimellitic acid, pyromellitic acid and anhydrides thereof, and polyhydric alcohols such as trimethylolpropane, trimethylolethane, glycerin, diglycerin, and pentaerythritol. Among them, trimethylol propane from the viewpoint of the reactivity at the time of thermal stability and polycondensation during film formation, trimellitic acid, pentaerythritol is preferred. These polyhydric carboxylic acids or polyhydric alcohols having a valency of 3 or more occupy A mole% of the polycarboxylic acid having a valency of 3 or more in the total acid component, When the ratio is B mol%, the total (A + B) of both is 0.01
-1 mol%, preferably 0.05-1 mol%. This is because if the total is less than 0.01 mol%, there is no effect of reducing shrinkage unevenness, and if it exceeds 1 mol%, gelation may occur during polymerization of the resin. The polyester resin of the present invention can be produced by a known direct polymerization method, transesterification method or the like.
Although the degree of polymerization is not particularly limited, the intrinsic viscosity (measured at 25 ° C. in a mixed solution of phenol / tetrachloroethane and the like) at 0.5 from the moldability of the film raw material.
-1.2 are preferred. The obtained polyester resin is formed into a heat-shrinkable polyester film by, for example, the following method. First, after drying the polyester resin, melt it,
A raw film is formed by melt extrusion from a die, casting or calendering. Next, the raw film was obtained from the glass transition temperature (Tg) of the polyester resin by 3.
At a temperature higher than 5 ° C., preferably at a temperature higher than 5 ° C., 1.5 to 5.0 times, preferably 1.0
It stretches up to 4.8 times to give a high shrinkage to the film. Further, if necessary, the film is stretched 1.0 to 1.8 times, preferably 1.0 to 1.5 times in the direction perpendicular to the stretching direction. This is effective for improving the tensile strength of the film and preventing the shrinkage in the stretching direction from being unnecessarily shrunk. The stretching of the film is performed by a method such as simultaneous biaxial stretching, sequential biaxial stretching, or uniaxial stretching. Either the longitudinal stretching or the transverse stretching may be performed first. The stretched heat-shrinkable polyester film can be used as a product as it is, but may be subjected to a heat treatment at a temperature of 50 to 150 ° C. for several seconds to several tens of seconds in view of dimensional stability and the like. By performing such a heat treatment,
Preferred properties such as adjustment of the shrinkage ratio in the shrinkage direction of the polyester film of the present invention, reduction of shrinkage over time during storage of the unshrinkable film, and reduction of shrinkage spots can be exhibited. The thickness of the heat-shrinkable polyester film of the present invention is not particularly limited.
The range is practically used. 6 to 380 μm for packaging applications, especially for packaging of foods, beverages, pharmaceuticals, etc.
Are used. When used for labels such as PET bottles, polyethylene bottles, and glass bottles, those having a range of 20 to 70 μm are used. The heat-shrinkable polyester film of the present invention has a shrinkage ratio of 5% or less when shrunk in hot air of 80 ° C. without load for 1 minute, and 1% in hot air of 120 ° C. without load. It is necessary that the contraction rate when contracted for 20 minutes is 20% or more. This is because, when the shrinkage ratio at 80 ° C. exceeds 5%, when shrinking at a high temperature of 120 ° C. or more, the heat-shrinkable film rapidly shrinks and causes uneven shrinkage. Has a shrinkage rate of 3 at 80 ° C.
% Or less. The shrinkage at 120 ° C. is 20
If it is less than 10%, a sufficient amount of shrinkage will not be obtained, and the adhesion of the film to the container will be insufficient, and it will be particularly difficult to completely cover a container or the like having a complicated shape. Considering the occurrence of uneven shrinkage due to rapid shrinkage when the film shrinks, the shrinkage at 120 ° C. is preferably in the range of 20 to 60%. In the present invention, conventionally known various processings and appropriate additives can be blended in order to further impart specific performance. Examples of processing include irradiation of ultraviolet rays, α-rays, β-rays, γ-rays, or electron beams, corona treatment, plasma irradiation treatment, flame treatment, and the like, vinylidene chloride, polyvinyl alcohol, polyamide, polyolefin, and the like. Application of a resin, lamination, vapor deposition of a metal, and the like are included. Examples of additives include polyamides,
Examples thereof include resins such as polyolefin, polymethyl methacrylate, and polycarbonate, inorganic particles such as silica, talc, kaolin, and calcium carbonate, pigments such as titanium oxide and carbon black, ultraviolet absorbers, release agents, and flame retardants. The present invention will be specifically described below with reference to examples. The shrinkage rate was set at 80 ° C. and 120 ° C. by providing marked lines at a distance of 100 mm on a polyester film cut into a size of 150 mm in the stretching direction and 20 mm in the direction perpendicular thereto.
When the film was allowed to stand in each hot air at 0 ° C. for 1 minute with no load, the length (L) before shrinkage and the length (L ′) after shrinkage were measured in the stretching direction of the film, and determined by the following equation. ## EQU1 ## Shrinkage ratio (%) = {(LL ′) / L} × 100 Shrinkage unevenness is 150 mm in the stretching direction and 2 in the perpendicular direction.
A polyester film cut into a size of 0 mm,
After heat shrinkage for 1 minute under no load in hot air at 120 ° C., the occurrence of uneven shrinkage on the film was visually observed. ○: Almost no uneven shrinkage was observed. Δ: Slight uneven shrinkage occurred. D: The evaluation was made in three stages, although the shrinkage unevenness was remarkable. Example 1 89.99 parts by mole of dimethyl naphthalenedicarboxylate, 10 parts by mole of dimethyl adipate, 0.01 part by mole of trimellitic anhydride and 200 parts by mole of ethylene glycol were placed in a reaction vessel, and acetic acid was used as a transesterification catalyst. Manganese was added at 400 ppm to the total acid components, and the transesterification reaction was sufficiently performed. Then, trimethyl phosphate as a stabilizer was added at 300 ppm based on the total acid components, and antimony trioxide was used as a polymerization catalyst at 400 ppm based on the total acid components.
pm, maintaining the temperature in the reaction vessel at 290 ° C.
A polycondensation reaction was performed for 3 hours under reduced pressure of 5 mmHg or less to obtain a polyester resin. After drying the obtained polyester resin, it was melt-extruded from a T-die at a resin temperature of 290 ° C. to prepare a raw film. This raw film is
Uniaxial stretching was performed 4.5 times in the stretching direction (TD direction) at 10 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of the measurement of the resin composition, shrinkage ratio, shrinkage unevenness, and solvent adhesion of the obtained film. Example 2 80 mol parts of dimethyl naphthalenedicarboxylate, 20 mol parts of dimethyl isophthalate, 200 mol parts of ethylene glycol, 15 mol parts of cyclohexanedimethanol and 0.05 mol part of trimethylolpropane were placed in a reaction vessel and transesterified. 400 ppm of manganese acetate was added as a catalyst to all acid components, and transesterification was sufficiently performed. Next, 300 ppm of trimethyl phosphate was added to the total acid component as a stabilizer, and 400 ppm of antimony trioxide was added to the total acid component as a polymerization catalyst. The temperature in the reaction vessel was maintained at 290 ° C., and 5 mmHg or less. A polycondensation reaction was performed for 3 hours under reduced pressure to obtain a polyester resin. After drying the obtained polyester resin, 290
It was melt-extruded from a T-die at a resin temperature of ° C. to prepare a raw film. This raw film was uniaxially stretched 4.5 times in the stretching direction (TD direction) at 110 ° C., and the thickness was 40 μm.
m of a heat-shrinkable polyester film was obtained. Resin composition of the obtained film, measurement results of shrinkage and shrinkage unevenness,
Table 1 shows the evaluation results of the solvent adhesiveness. Example 3 60 mol parts of dimethyl naphthalenedicarboxylate, 40 mol parts of dimethyl terephthalate, 200 mol parts of ethylene glycol and 0.5 mol part of trimethylolpropane were placed in a reaction vessel, and manganese acetate was converted to a total acid as a transesterification catalyst. 400 ppm was added to the components, and transesterification was sufficiently performed. Then, 300 ppm of trimethyl phosphate was added to the total acid component as a stabilizer, and 400 ppm of antimony trioxide was added to the total acid component as a polymerization catalyst. The temperature in the reaction vessel was maintained at 290 ° C., and 5 mm
A polycondensation reaction was performed for 3 hours under reduced pressure of Hg or less to obtain a polyester resin. After drying the obtained polyester resin, it was melt-extruded from a T-die at a resin temperature of 290 ° C. to prepare a raw film. 110 ° C
Perform uniaxial stretching 4.5 times in the stretching direction (TD direction) with
A heat-shrinkable polyester film having a thickness of 40 μm was obtained.
Table 1 shows the results of the measurement of the resin composition, shrinkage ratio, shrinkage unevenness, and solvent adhesion of the obtained film. Example 4 79 mol parts of dimethyl naphthalenedicarboxylate, 10 mol parts of dimethyl terephthalate, 10 mol parts of dimesyl isophthalate, 1 mol part of trimellitic anhydride, 200 mol parts of ethylene glycol and 10 mol parts of neopentyl glycol The mixture was placed in a reaction vessel, and 500 ppm of zinc acetate was added as a transesterification catalyst with respect to all the acid components, and transesterification was sufficiently performed. Then, trimethyl phosphate as a stabilizer was added at 300 ppm to the total acid component, and antimony trioxide was used as a polymerization catalyst at 500 ppm relative to the total acid component.
pm, titanium tetrabutoxide to the total acid component
Then, a polycondensation reaction was carried out for 3 hours under reduced pressure of 5 mmHg or less, and a polyester resin was obtained. After drying the obtained polyester resin, it was melt-extruded from a T-die at a resin temperature of 290 ° C. to prepare a raw film. This raw film was uniaxially stretched 4.5 times in the stretching direction (TD direction) at 110 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of the measurement of the resin composition, shrinkage ratio, shrinkage unevenness, and solvent adhesion of the obtained film. COMPARATIVE EXAMPLE 1 100 mol parts of dimethyl naphthalenedicarboxylate and 200 mol parts of ethylene glycol were placed in a reaction vessel, and manganese acetate was used as a transesterification catalyst in an amount of 400 parts based on all acid components.
ppm, and the transesterification reaction was sufficiently performed. Next, 300 ppm of trimethyl phosphate was added to the total acid component as a stabilizer, and 400 ppm of antimony trioxide was added to the total acid component as a polymerization catalyst. The temperature in the reaction vessel was maintained at 290 ° C., and 5 mmHg or less. A polycondensation reaction was performed for 3 hours under reduced pressure to obtain a polyester resin. After drying the obtained polyester resin, it was melt-extruded from a T-die at a resin temperature of 290 ° C. to prepare a raw film. This raw film was uniaxially stretched 4.5 times in the stretching direction (TD direction) at 110 ° C. to obtain a heat-shrinkable polyester film having a thickness of 40 μm. Table 1 shows the results of the measurement of the resin composition, shrinkage ratio, shrinkage unevenness, and solvent adhesion of the obtained film. Comparative Example 2 60 mol parts of dimethyl naphthalenedicarboxylate, 40 mol parts of dimethyl terephthalate and 200 mol parts of ethylene glycol were placed in a reaction vessel, and 400 ppm of magnesium acetate was added as a transesterification catalyst to the total acid components. The exchange reaction was fully performed. Next, trimethyl phosphate was added as a stabilizer at 300 p.
pm, antimony trioxide as a polymerization catalyst was added at 400 ppm to the total acid components, and the temperature in the reaction vessel was set to 290 ° C.
And a polycondensation reaction was performed for 3 hours under reduced pressure of 5 mmHg or less to obtain a polyester resin. After drying the obtained polyester resin, it was melt-extruded from a T-die at a resin temperature of 290 ° C. to prepare a raw film. This film was uniaxially stretched 4.5 times in the stretching direction (TD direction) at 110 ° C., but the mechanical strength of the film was weak and the film was broken during stretching. Comparative Example 3 60 mol parts of dimethyl naphthalenedicarboxylate, 40 mol parts of dimethyl terephthalate, 200 mol parts of ethylene glycol and 10 mol parts of pentaerythritol were placed in a reaction vessel, and magnesium acetate was used as a transesterification catalyst with respect to all acid components. And the transesterification reaction was sufficiently performed. Then, 300 ppm of trimethyl phosphate was added to the total acid component as a stabilizer, and 400 ppm of antimony trioxide was added to the total acid component as a polymerization catalyst. The temperature in the reaction vessel was maintained at 290 ° C., and 5 mm
Was subjected to polycondensation reaction by the following reduced pressure Hg, gelation in the course of the reaction takes place, a polyester resin makes possible the film as a film has not been obtained, et al. [Table 1] The components shown in the table are as follows. NDA: naphthalenedicarboxylic acid component TPA: terephthalic acid component IPA: isophthalic acid component ADA: adipic acid component TMA: trimellitic acid component EG: ethylene glycol component CHDM: cyclohexanedimethanol component NPG: neopentyl glycol component TMP: trimethylolpropane component The heat-shrinkable polyester film of the present invention has a high heat-shrinkage rate even at a relatively high temperature, has excellent shrink adhesion to containers such as bottles, and has a shrinkable coating having no shrinkage unevenness. It can be used and has excellent practicality as various packaging materials, and is particularly suitable as a heat-shrinkable label for glass bottles.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-25293 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 63/00-63/91

Claims (1)

(57) [Claim 1] A polyester resin comprising an acid component having naphthalenedicarboxylic acid or an ester-forming derivative thereof as a main component and an alcohol component having ethylene glycol as a main component. The ratio (A mol%) of the trivalent or higher polyvalent carboxylic acid in the total acid component to the ratio of the trivalent or higher polyvalent carboxylic acid in the total acid component (A mol%) Is contained in a range where the sum (A + B) of the ratio (B mol%) of the trihydric or higher polyhydric alcohol to the total is 0.01 to 1 mol%.
Then, when shrinking in hot air of 80 ° C for 1 minute,
5% or less and shrunk in hot air at 120 ° C for 1 minute
A heat shrinkable polyester film having a shrinkage factor of 20% or more .